Former City Councilman Jim Kenney, a late entry in the race for mayor, is getting a quick boost from outside groups airing television ads in his favor.

Forward Philadelphia, a new nonprofit funded in part by unionized teachers, on Wednesday will become the second "independent expenditure group" to run ads touting Kenney.

The new ad, a copy of which was obtained by The Inquirer, describes Kenney as "a progressive voice who will be mayor for our neighborhoods."

Forward Philadelphia will be funded by progressives, LGBT activists, and labor unions, according to a source familiar with the new nonprofit's plans.

One of those unions is the American Federation of Teachers. The national union representing educators in the Philadelphia School District confirmed Tuesday that it had contributed to the group.

The AFT's local chapter, the 12,000-member Philadelphia Federation of Teachers, endorsed Kenney two weeks ago.

"AFT proudly backs their choice of Jim Kenney to be the next mayor of Philadelphia," AFT President Randi Weingarten said in a statement when asked about Philadelphia Forward's new ad.

The new ad and the group behind it reflect two developments in mayoral politics: the rising role of outside spending by groups unbound by the city's tough campaign-donation caps, and the increasing electoral power of LGBT voters.

Kevin Vaughan, a former executive director of the city's Commission on Human Relations, is serving as the new group's chairman.

Vaughan, who was the first openly gay person to head a city agency, called Kenney "the right candidate at the right time." He declined to detail Forward Philadelphia's finances.

"Its part of the mix of how things are done at the moment," Vaughan said of independent expenditure groups. "I want to make sure that a candidate I'm proud of and who has done such a wonderful job in the city has the same kind of support as other candidates."

That was a veiled reference to American Cities, another independent expenditure group - which is expected to run ads in support of State Sen. Anthony H. Williams, another Democrat in the May 19 mayoral primary.

Such groups can spend above and beyond the city's contribution limits of $2,900 for individuals and $11,500 for political action committees as long as they don't coordinate with a campaign or candidate.

Williams started airing a campaign ad Tuesday, becoming the first candidate in the race to pay for his own time on television.

Campaign commercials this primary season have ranged from $150 for one 30-second spot on morning TV to $10,000 for an ad aired during the Villanova Wildcats' NCAA basketball tournament appearances.

Williams' campaign on Tuesday sent supporters this call for contributions:

"TV ads are expensive - and we need help to keep it on the air."

Kenney's campaign on Tuesday said he had no knowledge of Forward Philadelphia's plans.

The new group's political consultants include Bill Hyers, who ran Bill de Blasio's successful campaign for New York City mayor, President Obama's 2012 reelection efforts in Pennsylvania, and Mayor Nutter's first bid for mayor in 2007. The commercial was produced by Saul Shorr, who did Gov. Wolf's ads last year.

Building a Better Pennsylvania, a political action committee funded in the past by local building trades unions, two weeks ago started airing the first television commercials in the mayor's race - also in support of Kenney.

Still another reflection of the LGBT constituency's growing political power: Williams is scheduled to hold a news conference Wednesday with LGBT activists who support his campaign.

brennac@phillynews.com 215-854-5973 @byChrisBrennan